Beneficiation of potash ores



Nov. 14, 1961 A. ADAMS ETAL 3,008,655

BENEFICIATION OF POTASH ORES Filed May l1, 1959 3,008,655 Patented Nov. 14, 1961 3,008,655 BENEFICIATION OF POTASH ORES Albert Adams and William B. Dancy, Carlsbad, N. Mex.,

assignors to International Minerals & Chemical Corporation, a corporation of New York V Filed May 11, 1959, Ser. No. 812,414 8 Claims. (Cl. 241-20) The present invention generally relates to the beneficiation of potash ores. More particularly, it relates to an improved process for the recovery of sylvite from ores of the sylvinite type; `for example, such ores as are found in the Permain basin of the southwest area of the United States and mined chiefly in the Carlsbad district of New Mexico, and as are found in the Williston basin of the United States and Canada. The process is, however, applicable to the treatment of other potash ores wherein sylvite is associated with other minerals.

As is well known, potash is of great economic importance. Extensive deposits of potash salts are found on every continent. However, inpractically no instance is the potash salt `found in a substantially pure form. On the North American continent, one frequently encountered potash salt is sylvite (KCl). The KCl is not often found in any appreciable quantities as pure sylvite, but is most often found as sylvinite ore, which is a mixture of sylvite and halite (NaCl). A typical analysis of a sylvinite ore is as follows:

Percent Sylvite (KCl) 23 Halite (NaCl) 73 Other constituents or impurities consisting of silicates, sulfates, etc

The potash ore in the Williston basin also generally contains carnallite (KCl.MgCl2.6I-I2O).

Large amounts of sylvite are recovered from sylvinite ores by processes involving a froth flotation operation. In processes of this general character, it has been the general practice to grind the ore to a rather ne mesh size, for example, to a degree of lineness where at least 90% of the ore would pass through a sieve of about 40 mesh. Flotation of the valuable sylvite constituents from an ore of such a degree of iineness is not too diiiicult a problem, and various types of `collector agents for eifecting such iiotation can be used. In a sylvinite flotation process, the potash ore is slurried in a saturated brine solution to produce a brine slurry or pulp containing vfrom about 50% to about 75% solids. The pulp is Yreagentized with a suitable collector, diluted with brine, and passed to a flotation cell. In the flotation cell the pulp is kept in circulation and is Acontacted with air. Air bubbles adhere tothe reagentized sylvite particles and iloat the sylvite particles.k The sylvite oat is raked off of the top of the flotation cell. Not all of the sylvite is floated loi in the iirst otation cell and the remaining pulp is removed as underilow from the lirst cell and is passed to a second ilotation cell. In the second cell, the flotation operation is repeated, a sylvite concentrate is otated olf, and the remaining pulp may be passed to a third cell. A flotation machine usually contains a plurality, normally tive, 'of such cells associated togetherin series. After a series of flotation operations, the remaining pulp, from which substantial amounts of sylvite have been removed, is discarded as a tailing. This initial flotation operation is denominated a rougher flotation, the float product is denominated a rougher iloat'orl rougher concentrate, and the tai-ling is denominated a rougher t tail., Y

The rougher concentrate, while containing substantially all of the sylvite values in the charged pulp, also contains a substantial amount of line halite particles.`v Therefore, it is conventional practice to Ycombinethe rougher concentrate from the individual flotationy cells and subject the combined rougher concentrates to a cleaner otation operation. In the cleaner flotation operation, the rougher concentrate in a pulp is subjected to flotation in another plurality of otation cells in series. The unfloated pulp recovered from the last of the cleaner otation cells is denominated a mid or a middling and is usually recycled to the rougher cells. The float product from the cleaner operation is recovered as a high grade sylvite product, usually denominated a cleaner concentrate. i

The liotation of relatively large particles, however, is, in general, attended with considerably more diculty than when the particles are of relatively smaller size. In other words, it is generally more diflicult to float relatively larger size sylvite particles than it is to oat relatively smaller size particles. It has been observed that the large sylvite particles make up a substantial amount of the sylvite which is not floated and which is, therefore, usually 'lost in the tailings.

For many purposes, however, it is undesirable to reduce the mineral to a lvery small particle size. In the manufacture and Iutilization of fertilizers, for example, which commonly include phosphate rock and sylvite or other potash mineral, the use of such materials in finely divided form gives rise to caking and dusting problems, so that granular materials are distinctly preferred, `and the demand therefor has greatly expanded within recent years. A need has, therefore, existed for a method of beneficiating such minerals in granular for-m, so that they are directly available to the market without any necessity for separating them first in powdered form and then reconverting them into -granular tform.

Methods have already been devised which achieve otation of granular materials to some extent. 'Such methods generally subject an aqueous slurry of the desired material to flotation in the presence of a selective `collector reagent such as an amine or a fatty acid, a frothing agent such as an aliphatic alcohol of intermediate molecular Weight, and a non-saponifiable oil such as crude petroleum, fuel oil, or kerosene. Recently it has been discovered that the ilotation of granular materials is beneted when the otation mixture contains a viscous petroleum oil having certain characteristics. The viscous petroleum oil preferably has a viscosity at 130 F. greater than about SSU and a distillation range with a 10% point above about 500 F. (ASTM D-447). Many of the so-called gas oils, lubricating oil stocks, and paran or Wax distillates Obtained in the distillation of crude oils and in the redistillation of cracked stocks and heavy distillates have been found suitable.

It has been found by extensive study that the flotation of sylvite, especially granular sylvite, is markedly inhibited by the presence of slime-forming clay compounds. The term slimes, as used herein, includes Very line particles, such as clays. The term slimes is well known to those skilled in the art of beneiiciating potashrores and it is used herein as it is conventionally used in the art. The slimes associated with potash ores are, however, very difcult to remove. The present invention is concerned with the problem of providing a low slime content feed to a flotation operation.

Accordingly, it is an object of the present invention to provide a process for beneciating potash ore.`

' It is another object of the invention to provide a process for preparing a low slime content potash feed material. `It is a further object to provide a flotation process for the flotation of granular sylvite from sylvinite type ores; f

It lis an additional object to provide an improved process for the recovery of sylvite from sylvinite ores, which process includes a flotation operation and a desliming ste F1lhese and other objects and advantages of the present invention will be apparent to those skilled in the art as the description of the present invention progresses.

In accordance with the present invention, it has been discovered that eminently satisfactory beneficiation of potash ores and minerals can be achieved by means of a series of critical and interdependent process steps.

Generally described, the present invention is a process for beneficiating a potash ore which comprises subjecting a comminuted potash ore containing sylvite to a sizing treatment to provide at least two fractions, a first finer fraction composed principally of finer particles of said ore and a first coarser fraction comprised principally of coarser particles of said ore, separately comminuting the first coarser fraction, subjecting the comminuted coarser fraction to a sizing treatment to provide at least two fractions, a second finer fraction composed principally of finer particles of the comminuted first coarser fraction and a second coarser fraction composed principally of coarser particles of the comminuted first coarser fraction, combining at least a portion of the first finer fraction with at least a portion of the second finer fraction, separately conditioning at least a portion of the second coarser fraction with cationic collecting agent and then subjecting the combined finer fraction and the conditioned second coarser fraction to -frot-h flotation concentration.

In order to more fully appreciate the present invention with its many advantages, reference may be made to the accompanying drawing which is a diagrammatic flow-sheet illustrating the general application of the process of the invention.

In this novel process, potash ore containing sylvite, for example, sylvinite ore as received from the mine, is comminuted to economical liberation size to produce a granular feed material. The ore is comrninuted, usually dry crushed, to reduce substantially all of the ore to less than about P/s inch size. During the crushing to inch, a substantial portion of the ore is reduced to -20 mesh. It has been determined that the --201 mesh material contains the major portion of the liberated slimes, for example, 70% of the slimes in the ore, and, in accordance with the present invention, the comminuted ore is subjected to a sizing treatment to provide at least two fractions, a first finer fraction composed principally of finer particles of the comminuted ore and a first coarser fraction composed principally of coarser particles of the ore. The comrninuted ore is preferably sized on about 20 mesh so that the fine fractionis predominantly 420 mesh and the coarse fraction k+20 mesh. As hereinabove set forth, it has been determined that the -20 mesh material contains the major portion of the liberated slimes in the ore. Since the presence of slimes is particularly harmful in the flotation of granular sylvite, the materials in the first finer fraction are never again admixed with materials in the first coarser fraction until these materials are first conditioned for flotation. In other words, the first coarser fraction is treated in its own circuit, which usually is called the granular circuit, including the step of conditioning, and the first finer fraction is also separately treated in its own circuit, which usually is called the fines circuit, including the step of conditioning. After conditioning, the conditioned materials in the main processing streams may be admixed and then subjected to flotation or, alternately, the conditioned materials may be separately subjected to flotation. Further, when in any subsequent operation on the first coarser fraction, a relatively smaller size fraction is produced, for example, in a hydrocycloning and/or classification of `the material in the first coarser fraction, it is preferable that such smaller size fraction be removed 4 from contact with the coarser fra-ction until the coarser fraction is conditioned for flotation. These embodiments are illustrated in the accompanying drawing.

The comminuted ore from the crusher is slurried with a brine solution which is substantially saturated with respect to sylvite and also substantially saturated with respect to halite, and is then introduced into a classifier, termed the primary classifier, for the first sizing operation. For the sake of simplicity, and in order to present the invention in a clearer manner, the sizing in the primary classifier will be considered to be on 20 mesh. Sizing on 2() mesh is preferred since a beneficial split of slimes and sylvite is achieved on this size; however, it will be apparent to those skilled in the art that another mesh size may be used and it is, therefore, to be understood that the sizing may be on another predetermined mesh size. Also, in the subsequent description, which `may very readily be followed by referring to the drawing, certain mesh sizes are specified. These specified mesh sizes are also preferred; however, it will again be apparent to those skilled in the art that another mesh size may be used with equivalent results and it is, therefore, to be understood that the sizing may be on other predetermined mesh sizes. The other mesh sizes will preferably be close to the ymesn sizes specified in the description.

In the classifier, the operating conditions are maintained so as to obtain a pulp overflow composed principally of -20 mesh particles. This -20 mesh fraction is treated in its own fine circuit which is illustrated in the drawing chiefly in the left half of the drawing. The underflow from the classifier is composed principally of +20 mesh particles and is treated in its own granular circuit which is illustrated in the drawing chiefly in the right half of the drawing.

Directing attention rst to the treatment of the +20 mesh fraction, `this fraction also contains a substantial portion of +8 mesh material which is too large for eflcient flotation. The +20l mesh fraction is accordingly introduced into a so-called slime mill for wet grinding to reduce the coarser particles to a suitable size for a flotation feed. The wet grinding is preferably done in a rod mill since it has been determined that in a rod mill, very fine particles are not produced in too great an amount. The wet grinding operation is regulated so that the out flow from the rod mill is predominantly -8 `+20 mesh material. In general, it has been determined that the degree of size reduction depends, to some extent, upon one or more of the following: pulp density of the feed material, relationship between the volume of grinding media and the volume of the mill, the rod charge, the diameter of the rods, and the speed of the mill.

The discharge from the slime mill is introduced into a hydrocyclone, termed the granular hydrocyclone, for the removal of fines and liberated slimes produced in the slime mill. One or a bank of hydrocyclones in parallel may, of course, be used. The material is fed tangentially into the hydrocyclone. In the hydrocyclone a separation is made in the cone-shaped partby the action of centrifugal and centripetal forces. A discussion of hydrocyclones of this type may be found in Perry, Chemical Engineer-s Handbook, third edition. The cones are selected and operated to effect a separation on about 35 mesh. The 35 mesh material is removed as overflow from the hydrocyclone. This -35 mesh material usually contains a significant amount of slimes and is, therefore, in accordance with the invention, removed from the granular circuit. Accordingly, the -35 mesh material is removed from the granular circuit and is introduced with the -20 mesh overflow from the primary classifier into a primary hydroseparator in the fines circuit.

The +35 mesh underflow from the granular hydrocyclone is introduced into a secondary classifier for another sizing operation. In this secondary classifier, the operating conditions are maintained so as to obtain a pulp overflow composed principally of +20 mesh particles vand a pulp underflow composed principally of +20 mesh particles. Looking back at the operation of the granular cyclone, it should be noted that -35 mesh material is taken olf as overflow, and in the secondary classifier -20 mesh material is taken olf as overflow. Such an operation is preferred since it has been determined that improved results are obtained when treating the -35 mesh fraction and the -20 mesh fraction separately in the lines treating circuit. The further treatment accorded each of these fractions Will be described in detail hereinafter. It should, however, be noted at this time that the material in the -20 mesh overflow from the secondary classifier does not come into contact with any of the material in the granular circuit before the granular material is conditioned for flotation.

The -20 mesh overflow from the secondary classifier usually still contains some -200 mesh ore and slime particles. The -20 mesh material is, therefore, subjected to a sizing in a secondary hydrocyclone on about 48 mesh. Ihe -48 mesh overflow fraction from the secondary hydrocyclone is introduced into a second hydroseparator in the fines circuit hereinafter described in detail. The +48 mesh hydrocyclone underflow fraction contains predominantly -20 `+48 mesh particles. The +48 mesh fraction is substantially free of slimes and is passed to a nes conditioner for suitable conditioning for flotation.

The +20 mesh slurry underflow from the secondary classier is introduced into a granular conditioner wherein the material is treated with flotation reagents. For proper conditioning the material is preferably in the form of a relatively thick pulp, usually from about 50% to about 75% solid content, and when necessary, brine may be added to the `+20 mesh underflow. In the granular conditioner, the material is preferably conditioned with a cationic collector, a slime controllant and a viscous petroleum oil. A frothing agent may `also be added. These materials are conventionally employed in the flotation of sylvite and they are employed in conventional manner and amounts.

The cationic collector includes aliphatic amines such as n-lauryl amine. Other useful collector agents are high molecular Weight aliphatic amines of about C-l4 to C-20 length car-bon chains and their water-soluble acid addition salts, as well as quaternary ammonium salts, preferably the acetate or hydrochlorides, for example, octadecylamine acetate, hexadecylamine hydrochloride, and the like. High molecular weight aliphatic amines and their water-soluble acetate salts are commercially available. The collector floats potassium chloride particles. The slime controllant is also used in conventional manner and in conventional amount. Various slime control agents are known and starch is preferred. Other slime control agents are theV polyglycol and polyglycol ethers disclosed in U.S. Patent No. 2,724,499. Other slime control agents are sold by Dow Chemical Company and General Mills, Incorporated.

The viscous petroleum oil is also employed in conventional manner and in conventional amounts, generally between about 0.5 and about 5.0 pounds per ton of solids. It has been determined that a more selective and more complete flotation of the granular sylvite from the granular ore mixture is achieved by 'the use of the viscous petroleum oil. The oil preferably has a pourpoint of 50 F..to 100 F., a viscosity above about 100 S.S.U. at 130 F. and below 300 S.S.U., preferably above about 150 S.S.U. andshould be largely a high-boiling point material, having a distillation` temperature (ASTM D-447) above about 500 F. at the 10% Ydistillation level. A further description of suitable oils may be found in Trachta and Rodriguez co-pending patent application Serial No. 781,462, filed December 19, 1958.

. It is also conventional to incorporate in the flotation mixture a suitable frothing agent, such as an aliphatic alcohol of intermediate molecular weight (around C4-C10), a preferred example being methyl isobutyl carbinol. Other frothing agents are described in the art.

After conditioning, the slurry is diluted with brine to the desired degree for froth flotation, preferably to a solids concentration between about 20% and about 35% solids, and subjected to a froth flotation operation.

The fines circuit starts at the overflow from the primary classifier. The -20 mesh fraction overflowing from the primary classifier is introduced into a primary hydroseparator. The -35 mesh overflow from the granular hydrocyclone is also introduced into this primary hydroseparator. The primary hydroseparator is of a suitable type for slime removal. The rates of feed and agitation, as well as other operating variables, are so regulated during the desliming step as to insure an overflow which contains predominantly -200 mesh particles of the ore and the liberated insol'uble slimes. In general, -200 mesh sylvite particles are too small to be eiciently beneficiated in a froth flotation operation. The 200 mesh fraction is usually sent to brine clarification thickeners wherein the solids are permitted to settle out so that the clarified brine may be reused.

The +200 mesh underflow fraction from Ithe primary hydroseparator is then passed to a lines hydrocyclone for a sizing operation. In general, the +200 mesh material still contains -a considerable amount of liberated slimes land -200 mesh material. The fines hydrocyclone is selected and operated to effect a sizing on about 48 mesh. A hydrocyclone usually operates more efficiently at a solids content less than is present in the +200 mesh underflow fraction and, therefore, brine is usually added to dilute the +200 mesh fraction to the desired degree for hydrocycloning.

The +48 mesh underflow fraction from the fines hydrocyclone is sufficiently free of slimes to be amenable to conditioning and froth flotation. This material is accordingly passed, with other materials, into the fines yconditioner.

The -48 mesh overflow fraction from the nes hydrocyclone and the -48 mesh overflow from the secondary hydrocyclone are passed into a second hydroseparator. In thisY second hydroseparator, as in the primary hydroseparator, the rates of feed, agitation, and other operating lconditions are regula-ted so as to achieve deslirning or sizing at about 200 mesh. The -200 mesh overflow from the second hydroseparator is sent to brine clarification. The +200 mesh underflow is substantially free of slimes and other -200mesh material and is introduced into the fines conditioner.

In the lines conditioner, the material is treated with a slime controllant in conventional manner and in conventional amount.' Starch is a preferred slime controllant; hcn vvever, y other materials, for example the materials ldis- Cussed as slimeV control agents for the granular conditioning, may be used. When the conditioned nes material is combined with the condition granular material for flotation, a cationic agent need not be added to the lines conditioner. However, when the nes conditioned material is separately treated in its own line fraction flotation circuit, a cationic flotation reagent is also added to the conditioner. In general, the cationic agents suitable for such use are the same as those described for use in the granular conditioner. The aliphatic amines -for the -flne conditioning may be of relatively lower molecular weight as compared to the aliphatic amines used in the granular conditioning.

In a commercial operation, when the operation was changed from a conventional feed preparation process to the processnof the present invention, the production of V-8 +20 mesh granularV sylvite increased 40%.v

The following examples are given to illustrate the instant novel process and are not to be construed as limiti ing the invention thereto.

7 EXAMPLE r This example illustrates a specific commercial application of the invention.

A sylvinite ore as received from the mine had the fol- This ore was crushed to substantially all -3/8 inch size. 400 tons per hour of the crushed ore was slurried with a saturated brine solution to 42% solids and introduced into a primary classifier. The classifier was operated so as to produce about 100 tons per hour of 20 mesh overfiow (24% solids) and about 300 tons per hour of 20 mesh sands or underflow (70% solids). The +20 mesh sands or underfiow was introduced into a rod mill wherein the charge was comminuted to produce a predominantly -8 +20 mesh fraction. The discharge from the rod mill was introduced into a grandular hydrocyclone.

The granular hydrocyclone provided 5.0 tons per hour of a -35 mesh overfiow (16% solids) and 225 tons per hour `of a +35 mesh underflow. The +35 mesh underflow was introduced into a secondary classifier. The secondary classifier was operated to produce a substantially -20 mesh overliow at the rate of 55 tons per hour (8% solids) and a substantially +20 mesh sands or underflow at the rate of 170 tons per hour (70% solids). The +20 mesh fraction was passed to a granular conditioner and conditioned at 60% solids. This +20 mesh fraction contained only 0.08% slirnes. Potato starch was added to the solids in the conditioner at the rate of 0.3 pound per ton of solids. An amine flotation reagent, comprising a mixture of Armee TD, n-olctadecylamine, and Armee HTD, sold by Armour and Company, was then added to the conditioner at the rate of 2.20 pounds per ton of feed. A highly paraflinic, viscous, fractionator bottoms Inaterial produced lat the Maleo Oil Co. refinery at Artesia, New Mexico, was also introduced into the conditioner at the rate of 0.72 pound per ton of feed.

The -20 mesh overflow from the secondary classifier was passed to a secondary hydrocyclone which was operated to size at about 48 mesh. The -48 mesh overflow (3% solids) was removed at the rate off 215 tons per hour. The +48 mesh underfiow (70% solids) was 21 tons per hour. The +48 mesh fraction contained only 0.08% slimes vand Was sent to the nes conditioner.

Referring back to the primary classifier, the -20 mesh overflow was introduced into a primary hydroseparator along with the -35 mesh overflow from the granular hydrocyclone. The primary hydroseparator Was operated to produce a -200 mesh overflow (1.6% solids) at 510 tons per hour. The +200 mesh underflow (47% solids) at 180 tons per hour was diluted with fresh brine to 40% solids and then passed into a fines hydrocyclone.

The fines hydrocyclone was operated to size at about 48 mesh. The +48 mesh underflow (68% solids) at 53 tons per hour contained only 0.11% slimes, and was passed directly to the fines conditioner. The -48 mesh overfiow (22% solids) at 170 tons per hour from the fines hydrocyclone was introduced into a second hydroseparator along with the -48 mesh overiiow from the secondary hydrocyclonc.

The second hydroseparator -Was operated to remove a -200 mesh overflow (1.2% solids) at 330 tons per hour and a +200 mesh underflow (48% solids) at 110 tons per hour. The +200 mesh underow was passed to the fines conditioner.

Three main processing streams are, accordingly, being passed into the fines conditioner. From the second hydroseparator 52 tons per hour of +200 mesh material, from the secondary hydrocyclone 49 tons per hour of +48 mesh material, and from the lines hydrocyclone 110 tons per hour of +48 mesh material.

In the fines conditioner the material Was conditioned with potato starch, which was added to give 1.1 lbs. of starch per ton of solids.

The `conditioned fines material `at 211 tons per hour was combined with the conditioned granular material at tons per hour and the combined stream (381 tons per hour) was diluted with fresh brine to 28% solids and then passed through a conventional rougher .and cleaner flotation process. The sylvite product had a 61.6% K2O content and had the following analysis:

TABLE 1 K2O Mesh Size Analysis Analysis EXAMPLE II A sylvinite ore asreceived from the mine had the following analysis:

' Mineral analysis Percent Clay 1.0 Sylvite 22.0 I-Ialite and other minerals 77.0

In one operation, designated operation A, the rod mill discharge was recombined with the -20 mesh overflow frornthe primary classifier and the combined stream was then washed and classified on 20 mesh to produce -a substantially -20 mesh fraction and a substantially +20 mesh fraction. The +20 mesh fraction was passed to a conditioner and `conditioned at 60% solids with potato starch, amine, and the highly paraiiinic, viscous, fractionator bottom material, in substantially the same manner and amounts as the +20 mesh fraction described in EX- ample 'I was conditioned. The -20 mesh fraction was deslimed by washingand then separately conditioned with 1.1 lbs. of potato starch per ton of solids. The conditioned fractions were then combined and subjected to conventional froth flotation to produce a sylvite concentrate.

Operation B In another operation, designated operation B, which operation is in accordance with the process of this invention, the rod mill discharge was subjected to washing and classification on 20 mesh with the -20 mesh fraction from thisrclassification being combined with -20 mesh overflow Ifrom the primary classifier. The combined -20 mesh fraction was ideslimed by Washing and then conditioned with potato starch in substantially the same manner as the 20mesh fraction in operation A. The +20 mesh fraction was also yconditioned in substantially the same manner as the +20 mesh fraction in operation A. The conditioned fractions were then combined yand subjected to conventional froth flotation to produce Ia sylvite concentrate.

Comparing operations A and B, it may be noted that the primary difference in the processes is that in operation A, the rod mill discharge is combined with the primary classifier overflow and the combined stream is then classified to produce the -20 mesh fraction and the +20 mesh fraction which are separately subjected to conditioning prior to fiotation, while in operation B, the rod mill discharge is not first combined with the primary classifier overflow, but the rod mill discharge is classified to provide thev+20 mesh fraction which is separately condi -tioned and a +20 mesh fraction which is combined with the primary classifier overflow to provide the -20 mesh fraction which is separately conditioned.

The sylvite products from operations A and B were collected and analyzed. The results of the analysis and -a comparison of operations are shown below in Table 2.

From Table 2, it may be seen that when following operation B, which is in accordance with the present invention, more +20 material was in the product and, further, the overall KZO content of the product was higher.

The description of the invention utilized specific reference to `certain process details; however, it is to be understood that such details are illustrative only and not by way of limitation. Other modifications and equivalents of the invention will be apparent to those skilled in the art from the foregoing description.

Having now fully described and illustrated the invention, what is desired to be secured and claimed by Letters Patent is set forth in the appended claims:

1. A process for beneciating `a potash ore which comprises subjecting a comminuated potash ore containing sylvite to a sizing treatment to provide at least two fractions, a first finer fraction composed principally of finer particles of said ore and -a rst coarser fraction composed principally of coarser particles of said ore, separately comminuting the first coarser fraction, separately subjecting the comminuted coarser fraction to a sizing treatment to provide at least two fractions, a second finer fraction composed principally of finer particles of the comminuted first coarser fraction land a second coarser fraction composed principally of coarser particles of the comminuted first coarser fraction, combining at least a portion of the first finer fraction with at least a portion of the second finer fraction, conditioning the combined finer fraction with Ia slime controllant, separately conditioning at least a portion of the second coarser fraction with a cationic collecting agent and then subjecting the conditioned combined finer fraction and the conditioned second coarser fraction to froth fiotation concentration.

2. A process for beneficiating a potash ore which comprises comminuting a potash ore containing sylvite to reduce substantially all of the ore to less than about 1%; inch size, subjecting the comminuted potash ore to a sizing treatment to provide at least two fractions, a first finer fraction composed principally of -20 mesh particles of said ore and a first coarser fraction composed principally of +20 mesh particles of said ore, separately comminuting the rst coarser fraction, separately subjecting the comminuted coarser fraction to ya sizing treatment to prov-ide at least two fractions, a second finer fraction composed principally of finer particles of the comminuted first coarser fraction and a second coarser fraction composed principally of coarser particles of the comminuted first coarser fraction, combining at least a portion of the first finer fraction with at least a portion of the second finer fraction, conditioning the combined finer fraction with a slime controllant, separately condi- Y r Y 10 tioning at least a portion of the second coarser fraction with a` cat-ionic collecting agent and then subjecting the conditioned combined finer fraction and the conditioned second coarser fraction to froth fiotation concentration.

3. A process for beneficiating a potash ore which comprises comminuting a potash ore containing sylvite to reduce substantially all of the ore to less than about inch size, subjecting the comminuted potash ore to a sizing treatment to provide at least two fractions, a first finer fraction composed principally of -20 mesh particles of said ore and a first coarser fraction composed principally of +20 mesh particles of said ore, separately comminuting the first coarser fraction to substantially all -8 mesh size particles, separately subjecting the comminuted coarser fraction to a sizing treatment to provide at least two fractions, a second finer fraction composed principally of -20 mesh particles of the comminuted first coarser fraction and a second coarser fraction composed principally of +20 mesh particles of the comminuted first coarser fraction, combining at least a portion of the first finer fraction with at least a portion of the second finer fraction, conditioning the combined finer fraction with arslime controllant, separately conditioning at least a portion of the second coarser fraction with a cationic collecting agent and then subjecting the conditioned combined finer fraction and the conditioned second coarser fraction to froth flotation concentration. f

4. A process for beneficiating a potash ore which cornprises subjecting a comminuted potash ore containing sylvite to a sizing treatment to provide at least two fractions, a first finer fraction composed principally of finer particles of said ore and a first coarser fraction composed principally of coarser particles of said ore, separately comminuting the first coarser fraction, separately subjecting the comminuted coarser fraction to a sizing treatment to provide at least two fractions, a second finer fraction composed principally of finer particles of the comminuted first coarser fraction and a second coarser fraction composed principally of coarser particles of the comminuted first coarser fraction, combining at least a portion of the first finer fraction with at least a portion of the second finer fraction, separately conditioning at least a portion of the second coarser fraction with a cationic collecting agent and subjecting the conditioned second coarser fraction to froth flotation concentration, and separately conditioning at least a portion of the combined finer fraction with a cationic collecting agent =and subjecting the conditioned combined finer `fraction to froth fiotation concentration.

5. A process for beneficiating a potash ore which comprises subjecting a comminuted potash ore containing sylvite to a sizing treatment to provide at least two fractions, a first finer fraction composed principally of finer particles of said ore and a first coarser fraction composed principally of coarser particles lof said ore, separately comminuting the rst coarser fraction, `separately subjeoting the comminuted coarser fraction to a sizing treatnient to provide at least two fractions, a second finer fraction composed principally of finer particles of the comminuted first coarser fraction and a second coarser fraction composed principally of coarser particles of the comminuted first coarser fraction, combining at least a portion of the first finer fraction with at least a portion of the second finer fraction, conditioning the combined finer fraction with a slime controllant, separately conditioning at least a portion of the second coarser fraction with a cationic collecting agent, combining at least a portion of the conditioned combined finer fraction with at least -a portion of the conditioned second coarser fraction, and then subjecting the combined fractions to froth fiotation concentration.

6. A process for beneficiating a potash ore which comprises subjecting a comminuted potash ore containing sylvite to a sizing treatment to provide at least two fractions, a first finer fraction composed principally of finer particles of said ore `and a first coarser fraction composed principally of coarser particles `of said ore, separately comminuting the first coarser fraction, separately subjecting the comminuted coarser fraction to a sizing treatment to provide at least two fractions, a second finer fraction composed principally of finer particles of the comminuted first coarser fraction and a second coarser fraction composed principally of coarser particles of the comminuted first coarser fraction, combining `at least a pontion of the first finer fraction with at least a portion of the second nner fraction, separately conditioning at least a portion of the second coarser fraction with a cationic collecting agent and separately conditioning at least a portion of the finer fraction with starch, combining at least a portion of the starch conditioned combined finer fraction with at least a portion of the conditioned second coarser fraction, and then subjecting the combined coarser and ner fraction to froth otation concentration, and recovering a sylvite concentrate.

7. A process for beneficiating a potash ore which comprises comminuting a potash `ore containing sylvite to reduce substantially all of the ore to less than about 1%; inch size, subjecting the comminuted potash ore to a sizing treatment to provide at least two fractions, `a first iiner fraction composed principally of -20 mesh particles of said yore and a first coarser fraction composed principally of |20 mesh particles of said ore, separately comminuting the first coarser fraction, separately subjecting the comminuted coarser fraction to a sizing treatment to provide at least two fractions, a second finer fraction composed principally of ner particles of the comminuted rst coarser fraction and a second coarser fraction cornposed principally of coarser particles of the comminuted first coarser fraction, combining at least a portion of the first finer fraction with at least a pon-tion of the second ner fraction, separately conditioning at least a portion of the second coarser fraction with a cationic collecting agent and separately conditioning at least a portion of the finer fraction with starch, combining at least a portion of the starch conditioned combined finer fraction with at least a portion of the conditioned second coarser fraction, and then subjecting the combined coarser and finer fraction to froth flotation concentration, and recovering a sylvite concentrate.

8. A process for beneficiating a potash ore which comprises comminuting a potash ore containing sylvite to reduce substantially all of the ore to less than about inch size, subjecting the comminuted potash ore to a sizing treatment to provide at least two fractions, `a irst finer fraction composed principally of -20 mesh particles of said ore and a rst coarser fraction composed principally of +20 mesh particles of said ore, separately comminuting the first coarser fraction to substantially all- -8 mesh size particles, separately subjecting the comminuted coarser fraction to a sizing treatment to provide at least two fractions, a second finer lfraction composed principally of -20 mesh particles of the comminuted irst coarser fraction -and a second coarser inaction composed principally of +20 mesh particles of Ithe comminuted first coarser fraction, combining at least a portion of the first finer fraction with at least a fraction of the second finer portion, separately conditioning at least `a portion of the second coarser `fraction With `an amine collecting agent and separately conditioning yat least a portion of the finer fraction with starch, combining at least a portion `of the starch conditioned combined finer fraction with at least a portion of the conditioned second coarser fraction, and then subjecting the combined coarser and finer fraction to froth flotation concentration and recovering a sylvite concentrate.

References Cited in the file of this patent UNlTED STATES PATENTS 

1. A PROCESS FOR BENEFICATING A POTASH ORE WHICH COMPRISES SUBJECTING A COMMINUATED POTASH ORE CONTAINING SYLVITE TO A SIZING TREATMENT TO PROVIDE AT LEAST TWO FRACTIONS, A FIRST FINER FRACTION COMPOSED PRINCIPALLY OF FINER PARTICLES OF SAID ORE AND A FIRST COARSER FRACTION COMPOSES PRINCIPALLY OF COARSER PARTICLES OF SAID ORE, SEPARATELY COMMINUTING THE FIRST COARSER FRACTION, SEPARATELY SUBJECTING THE COMMINUTED COARSER FRACTION TO A SIZING TREATMENT TO PROVIDE AT LEAST TWO FRACTIONS, A SECOND FINER FRACTION COMPOSED PRINCIPALLY OF FINER PARTICLES OF THE COMMINUTED FIRST COARSER FRACTION AND A SECOND COARSER FRACTION COMPOSED PRINCIPALLY OF COARSER PARTICLES OF THE COMMINUTED FIRST COARSER FRACTION, COMBINING AT LEAST A PORTION OF THE FIRST FINER FRACTION WITH AT LEAST A PORTION OF THE SECOND FINER FRACTION, CONDITIONING THE COMBINED FINER FRACTION WITH A SLIME CONTROLLANT, SEPARATELY CONDITIONING AT LEAST A PORTION OF THE SECOND COARSER FRACTION WITH A CATIONIC COLLECTING AGENT AND THEN SUBJECTING THE CONDITIONED COMBINED FINER FRACTION AND THE CONDITIONED SECOND COARSER FRACTION TO FROTH FLOTATION CONCENTRATION. 